Memory arrays comprising strings of memory cells and methods used in forming a memory array comprising strings of memory cells

ABSTRACT

A memory array comprising strings of memory cells comprises an upper stack above a lower stack. The lower stack comprises vertically-alternating lower conductive tiers and lower insulative tiers. The upper stack comprises vertically-alternating upper conductive tiers and upper insulative tiers. An intervening tier is vertically between the upper and lower stacks. The intervening tier is at least predominantly polysilicon and of different composition from compositions of the upper conductive tier and the upper insulative tier immediately-above the intervening tier and of different composition from compositions of the lower conductive tier and the lower insulative tier immediately-below the intervening tier. Channel-material strings of memory cells extend through the upper stack, the intervening tier, and the lower stack. Other structures and methods are disclosed.

TECHNICAL FIELD

Embodiments disclosed herein pertain to memory arrays and to methods used in forming a memory array.

BACKGROUND

Memory is one type of integrated circuitry and is used in computer systems for storing data. Memory may be fabricated in one or more arrays of individual memory cells. Memory cells may be written to, or read from, using digitlines (which may also be referred to as bitlines, data lines, or sense lines) and access lines (which may also be referred to as wordlines). The sense lines may conductively interconnect memory cells along columns of the array, and the access lines may conductively interconnect memory cells along rows of the array. Each memory cell may be uniquely addressed through the combination of a sense line and an access line.

Memory cells may be volatile, semi-volatile, or non-volatile. Non-volatile memory cells can store data for extended periods of time in the absence of power. Non-volatile memory is conventionally specified to be memory having a retention time of at least about 10 years. Volatile memory dissipates and is therefore refreshed/rewritten to maintain data storage. Volatile memory may have a retention time of milliseconds or less. Regardless, memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.

A field effect transistor is one type of electronic component that may be used in a memory cell. These transistors comprise a pair of conductive source/drain regions having a semiconductive channel region there-between. A conductive gate is adjacent the channel region and separated there-from by a thin gate insulator. Application of a suitable voltage to the gate allows current to flow from one of the source/drain regions to the other through the channel region. When the voltage is removed from the gate, current is largely prevented from flowing through the channel region. Field effect transistors may also include additional structure, for example a reversibly programmable charge-storage region as part of the gate construction between the gate insulator and the conductive gate.

Flash memory is one type of memory and has numerous uses in modern computers and devices. For instance, modern personal computers may have BIOS stored on a flash memory chip. As another example, it is becoming increasingly common for computers and other devices to utilize flash memory in solid state drives to replace conventional hard drives. As yet another example, flash memory is popular in wireless electronic devices because it enables manufacturers to support new communication protocols as they become standardized, and to provide the ability to remotely upgrade the devices for enhanced features.

NAND may be a basic architecture of integrated flash memory. A NAND cell unit comprises at least one selecting device coupled in series to a serial combination of memory cells (with the serial combination commonly being referred to as a NAND string). NAND architecture may be configured in a three-dimensional arrangement comprising vertically-stacked memory cells individually comprising a reversibly programmable vertical transistor. Control or other circuitry may be formed below the vertically-stacked memory cells. Other volatile or non-volatile memory array architectures may also comprise vertically-stacked memory cells that individually comprise a transistor.

Memory arrays may be arranged in memory pages, memory blocks and partial blocks (e.g., sub-blocks), and memory planes, for example as shown and described in any of U.S. Patent Application Publication Nos. 2015/0228651, 2016/0267984, and 2017/0140833. The memory blocks may at least in part define longitudinal outlines of individual wordlines in individual wordline tiers of vertically-stacked memory cells. Connections to these wordlines may occur in a so-called “stair-step structure” at an end or edge of an array of the vertically-stacked memory cells. The stair-step structure includes individual “stairs” (alternately termed “steps” or “stair-steps”) that define contact regions of the individual wordlines upon which elevationally-extending conductive vias contact to provide electrical access to the wordlines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view of a portion of a substrate in process in accordance with an embodiment of the invention and is taken through line 1-1 in FIG. 2.

FIG. 2 is a diagrammatic cross-sectional view taken through line 2-2 in FIG. 1.

FIG. 3 is an enlarged view of a portions of FIGS. 1 and 2.

FIGS. 4-20 are diagrammatic sequential sectional, expanded, enlarged, and/or partial views of the construction of FIGS. 1-3, or portions thereof, in process in accordance with some embodiments of the invention.

FIG. 21 shows an alternate example method and/or structural embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the invention encompass methods used in forming a memory array, for example an array of NAND or other memory cells that may have at least some peripheral control circuitry under the array (e.g., CMOS-under-array). Embodiments of the invention encompass so-called “gate-last” or “replacement-gate” processing, so-called “gate-first” processing, and other processing whether existing or future-developed independent of when transistor gates are formed. Embodiments of the invention also encompass a memory array (e.g., NAND architecture) independent of method of manufacture. First example method embodiments are described with reference to FIGS. 1-20 which may be considered as a “gate-last” or “replacement-gate” process, and starting with FIGS. 1-3.

FIGS. 1-3 show a construction 10 having an array or array area 12 in which elevationally-extending strings of transistors and/or memory cells will be formed. Construction 10 comprises a base substrate 11 having any one or more of conductive/conductor/conducting, semiconductive/semiconductor/semiconducting, or insulative/insulator/insulating (i.e., electrically herein) materials. Various materials have been formed elevationally over base substrate 11. Materials may be aside, elevationally inward, or elevationally outward of the FIGS. 1-3-depicted materials. For example, other partially or wholly fabricated components of integrated circuitry may be provided somewhere above, about, or within base substrate 11. Control and/or other peripheral circuitry for operating components within an array (e.g., array 12) of elevationally-extending strings of memory cells may also be fabricated and may or may not be wholly or partially within an array or sub-array. Further, multiple sub-arrays may also be fabricated and operated independently, in tandem, or otherwise relative one another. In this document, a “sub-array” may also be considered as an array.

A conductor tier 16 comprising conductor material 17 (e.g., conductively-doped polysilicon atop WSi_(x)) has been formed above substrate 11. Conductor tier 16 may comprise part of control circuitry (e.g., peripheral-under-array circuitry and/or a common source line or plate) used to control read and write access to the transistors and/or memory cells that will be formed within array 12.

A lower stack 18L comprising vertically-alternating lower insulative tiers 20L and lower conductive tiers 22L has been formed above conductor tier 16. Example thickness for each of lower tiers 20L and 22L is 22 to 60 nanometers. Only a small number of lower tiers 20L and 22L is shown, with more likely lower stack 18L comprising dozens, a hundred or more, etc. of lower tiers 20L and 22L. Other circuitry that may or may not be part of peripheral and/or control circuitry may be between conductor tier 16 and lower stack 18L. For example, multiple vertically-alternating tiers of conductive material and insulative material of such circuitry may be below a lowest of lower conductive tiers 22L and/or above an uppermost of lower conductive tiers 22L. For example, one or more select gate tiers (not shown) or dummy tiers (not shown) may be between conductor tier 16 and the lowest conductive tier 22L and one or more select gate tiers (not shown) or dummy tiers (not shown) may be above an uppermost of lower conductive tiers 22L. Alternately or additionally, at least one of the depicted lowest conductive tiers 22L may be a select gate tier. Regardless, lower conductive tiers 22L (alternately referred to as lower first tiers) may not comprise conducting material and lower insulative tiers 20L (alternately referred to as lower second tiers) may not comprise insulative material or be insulative at this point in processing in conjunction with the hereby initially-described example method embodiment which is “gate-last” or “replacement-gate”. Example lower conductive tiers 22L comprise first material 26 (e.g., silicon nitride) which may be wholly or partially sacrificial. Example lower insulative tiers 20L comprise second material 24 (e.g., silicon dioxide) that is of different composition from that of first material 26 and which may be wholly or partially sacrificial.

An intervening tier 21 is above lower stack 18L and is further characterized below.

Lower channel openings 25 have been formed (e.g., by etching) through intervening tier 21, lower insulative tiers 20L and lower conductive tiers 22L to conductor tier 16. Lower channel openings 25 may taper radially-inward (not shown) moving deeper into lower stack 18L. In some embodiments, lower channel openings 25 may go into conductor material 17 of conductor tier 16 as shown or may stop there-atop (not shown). Alternately, as an example, lower channel openings 25 may stop atop or within the lowest lower insulative tier 20L. A reason for extending lower channel openings 25 at least to into conductor material 17 of conductor tier 16 is to provide an anchoring effect to material that is within lower channel openings 25. Etch-stop material (not shown) may be within or atop conductor material 17 of conductor tier 16 to facilitate stopping of the etching of lower channel openings 25 relative to conductor tier 16 when such is desired. Such etch-stop material may be sacrificial or non-sacrificial. Regardless, lower channel openings 25 may be considered as having an average longitudinal axis 75 (e.g., average if axis 75 is not perfectly straight) that in one embodiment is vertical.

Horizontally-elongated lower trenches 40L have been formed (e.g., by anisotropic etching) into intervening tier 21 and lower stack 18L to form laterally-spaced memory-block regions 58. By way of example and for brevity only, lower channel openings 25 are shown as being arranged in groups or columns of staggered rows of four and five lower channel openings 25 per row and being arrayed in laterally-spaced memory-block regions 58 that will comprise laterally-spaced memory blocks 58 in a finished circuitry construction. In this document, “block” is generic to include “sub-block”. Lower trenches 40L will typically be wider than lower channel openings 25 (e.g., 10 to 20 times wider, yet such wider degree not being shown for brevity). Memory-block regions 58 and resultant memory blocks 58 (not yet shown) may be considered as being longitudinally elongated and oriented, for example along a direction 55. Any alternate existing or future-developed arrangement and construction may be used.

Sacrificial material 59 has been formed in lower channel openings 25 in intervening tier 21, in lower first tiers 22L, and in lower second tiers 20L. In one embodiment and as shown, sacrificial material 59 has been formed in lower trenches 40L. In one embodiment, sacrificial material 59 in lower channel openings 25 comprises a radially-outer silicon dioxide 70, a radially-inner silicon dioxide 72, and aluminum oxide 71 radially-between radially-outer silicon dioxide 70 and radially-inner silicon dioxide 72. Lower trenches 40L may comprise corresponding aluminum oxide 71 and silicon dioxide 70, 72. Materials 70, 71, and 72 are only so designated in FIG. 3 for clarity in other figures. In one embodiment, radially-outer silicon dioxide 70 and radially-inner silicon dioxide 72 are of different composition relative one another, and in one such embodiment the different composition is characterized by concentration of at least one of boron and phosphorus. As but one specific example, radially-inner silicon dioxide 72 is BPSG and radially-outer silicon dioxide 70 is undoped silicon dioxide.

Referring to FIG. 4, an upper stack 18U comprising vertically-alternating upper insulative tiers 20U (alternately referred to as upper second tiers) and upper conductive tiers 22U (alternately referred to as upper first tiers) has been formed above intervening tier 21 and lower stack 18L. Upper insulative tiers 20U and upper conductive tiers 22U may have any of the attributes described above with respect to lower insulative tiers 20L and lower conductive tiers 22L. Example upper conductive tiers 22U comprise first material 26 (e.g., silicon nitride) which may be wholly or partially sacrificial. Example upper insulative tiers 20U are shown as comprising second material 24 and upper conductive tiers 22U are shown as comprising first material 26, although other compositions may of course be used and not necessarily of the same composition as in lower stack 18L.

In some embodiments, intervening tier 21 is at least one of (a), (b), and (c), where:

-   -   (a): of a thickness greater (e.g., at least two times, three         times being shown) than that of the upper first tier 22U and         that of the upper second tier 20U immediately-above intervening         tier 21 and greater than that of the lower first tier 22L and         that of the lower second tier 20L immediately-below intervening         tier 21;     -   (b): at least predominantly polysilicon and of different         composition from compositions of the upper first tier 22U and         the upper second tier 20U immediately-above intervening tier 21         and of different composition from compositions of the lower         first tier 22L and the lower second tier 20L immediately-below         intervening tier 21; and     -   (c): at least predominantly conductive and of different         composition from the compositions of the upper first tier 22U         and the upper second tier 20U immediately-above intervening tier         21 and of different composition from the compositions of the         lower first tier 22L and the lower second tier 20L         immediately-below intervening tier 21.         In one embodiment, intervening tier 21 is (a); in one embodiment         is (b); in one embodiment is (c); in one embodiment is at least         two of (a), (b), and (c); and in one embodiment is (a), (b), and         (c).

If (b) or including (b), in one embodiment, intervening tier 21 is at least predominantly undoped polysilicon (i.e., “undoped” in the context of polysilicon being with reference to conductivity-increasing impurity and meaning from 0 atoms/cm³ to 1×10¹² atoms/cm³). If (b) or including (b), in one embodiment, intervening tier 21 is at least predominantly doped polysilicon (i.e., “doped” in the context of polysilicon being with reference to conductivity-increasing impurity and meaning from greater than 1×10¹² atoms/cm³ to 1×10³⁰ atoms/cm³), in one such embodiment being at least predominantly semiconductively-doped polysilicon (e.g., from at least 1×10¹⁴ atoms/cm³ to less than 1×10²¹ atoms/cm³), and in another such embodiment being at least predominantly conductively-doped polysilicon (e.g., from at least 1×10²¹ atoms/cm³ to 1×10³⁰ atoms/cm³).

If (c) or including (c), in one embodiment, intervening tier 21 is at least predominantly at least one of an elemental metal, a metal alloy, a metal nitride, and a metal silicide. In another embodiment, if (c) or including (c), intervening tier 21 is at least predominantly conductively-doped semiconductive material.

Referring to FIGS. 5-7, upper channel openings 39 have been formed (e.g. by etching) through upper first tiers 22U and upper second tiers 20U to intervening tier 21, with individual upper channel openings 39 extending to sacrificial material 59 that is in individual lower channel openings 25. In one embodiment and as shown, and as may be best perceived with reference to FIGS. 6 and 7, individual upper channel openings 39 are formed to have an average longitudinal axis 85 that is angled by an angle A from average longitudinal axis 75 of their respective individual lower channel opening 25 to which they extend. In one embodiment, such angling is at an angle A of at least 0.5° from average longitudinal axis 75, in one such embodiment at an angle A of no more than 5.0° from average longitudinal axis 75, and in one such embodiment at an angle A of at least 1.0° to no more than 5.0° from average longitudinal axis 75 (4° being shown). Regardless, if forming upper channel openings 39 by etching, some etching (not shown) may occur into lower sacrificial material 59, intervening material, and/or into uppermost tiers

Referring to FIGS. 8 and 9, sacrificial material 59 (i.e., at least some) has been removed (e.g., by etching) from individual lower channel openings 25 through upper channel openings 39. Where, for example, materials 70, 71, and 72 are present, some of 70 and/or 71 may remain to facilitate formation of transistor material (described below).

Transistor channel material may be formed in the individual channel openings elevationally along the insulative tiers and the conductive tiers, thus comprising individual channel-material strings, which is directly electrically coupled with conductive material in the conductor tier. Individual memory cells of the example memory array being formed may comprise a gate region (e.g., a control-gate region) and a memory structure laterally-between the gate region and the channel material. In one such embodiment, the memory structure is formed to comprise a charge-blocking region, storage material (e.g., charge-storage material), and an insulative charge-passage material. The storage material (e.g., floating gate material such as doped or undoped silicon or charge-trapping material such as silicon nitride, metal dots, etc.) of the individual memory cells is elevationally along individual of the charge-blocking regions. The insulative charge-passage material (e.g., a band gap-engineered structure having nitrogen-containing material [e.g., silicon nitride] sandwiched between two insulator oxides [e.g., silicon dioxide]) is laterally-between the channel material and the storage material.

FIGS. 10-13 show one embodiment wherein charge-blocking material 30, storage material 32, and charge-passage material 34 have been formed in individual upper channel openings 39 and lower channel openings 25 elevationally along insulative tiers 20 and conductive tiers 22. Transistor materials 30, 32, and 34 (e.g., memory-cell materials) may be formed by, for example, deposition of respective thin layers thereof over upper stack 18U and within individual openings 39 and 25 followed by planarizing such back at least to a top surface of upper stack 18U.

Channel material 36 has also been formed in channel openings 39/25 elevationally along insulative tiers 20U/20L and conductive tiers 22U/22L, thus comprising individual operative channel-material strings 53 in channel openings 39/25. Channel-material strings 53 in one embodiment have memory-cell materials (e.g., 30, 32, and 34) there-along and with second-tier material (e.g., 24) being horizontally-between immediately-adjacent channel-material strings 53. Materials 30, 32, 34, and 36 are collectively shown as and only designated as material 37 in FIGS. 10 and 11 due to scale. Example channel materials 36 include appropriately-doped crystalline semiconductor material, such as one or more silicon, germanium, and so-called III/V semiconductor materials (e.g., GaAs, InP, GaP, and GaN). Example thickness for each of materials 30, 32, 34, and 36 is 25 to 100 Angstroms. Punch etching may be conducted to remove materials 30, 32, and 34 from the bases of lower channel openings 25 (not shown) to expose conductor tier 16 such that channel material 36 is directly against conductor material 17 of conductor tier 16. Such punch etching may occur separately with respect to each of materials 30, 32, and 34 (as shown) or may occur with respect to only some (not shown). Alternately, and by way of example only, no punch etching may be conducted and channel material 36 may be directly electrically coupled to conductor material 17 of conductor tier 16 only by a separate conductive interconnect (not yet shown). Channel openings 39/25 are shown as comprising a radially-central solid dielectric material 38 (e.g., spin-on-dielectric, silicon dioxide, and/or silicon nitride). Alternately, and by way of example only, the radially-central portion within channel openings 39/25 may include void space(s) (not shown) and/or be devoid of solid material (not shown).

Referring to FIGS. 14 and 15, horizontally-elongated upper trenches 40U have been formed to lower trenches 40L and sacrificial material 59 (not shown) has then been removed therefrom (e.g., by selective etching).

Referring to FIGS. 16-20, material 26 (not shown) of conductive tiers 22U/22L has been removed, for example by being isotropically etched away through trenches 40U/40L ideally selectively relative to the other exposed materials (e.g., using liquid or vapor H₃PO₄ as a primary etchant where material 26 is silicon nitride and other materials comprise one or more oxides or polysilicon). Material 26 (not shown) in conductive tiers 22U/22L in the example embodiment is sacrificial and has been replaced with conducting material 48, and which has thereafter been removed from trenches 40U/40L, thus forming individual conductive lines 29 (e.g., wordlines) and elevationally-extending strings 49 of individual transistors and/or memory cells 56.

A thin insulative liner (e.g., Al₂O₃ and not shown) may be formed before forming conducting material 48. Approximate locations of transistors and/or memory cells 56 are indicated with a bracket in FIG. 19 and some with dashed outlines in FIGS. 16-18 and 20, with transistors and/or memory cells 56 being essentially ring-like or annular in the depicted example. Alternately, transistors and/or memory cells 56 may not be completely encircling relative to individual channel openings 39/25 such that each channel opening 39/25 may have two or more elevationally-extending strings 49 (e.g., multiple transistors and/or memory cells about individual channel openings in individual conductive tiers with perhaps multiple wordlines per channel opening in individual conductive tiers, and not shown). Conducting material 48 may be considered as having terminal ends 50 (FIG. 19) corresponding to control-gate regions 52 of individual transistors and/or memory cells 56. Control-gate regions 52 in the depicted embodiment comprise individual portions of individual conductive lines 29. Materials 30, 32, and 34 may be considered as a memory structure 65 that is laterally between control-gate region 52 and channel material 36. In one embodiment and as shown with respect to the example “gate-last” processing, conducting material 48 of conductive tiers 22U/22L is formed after forming channel openings 39/25 and/or trenches 40U/40L. Alternately, the conducting material of the conductive tiers may be formed before forming channel openings 39/25 and/or trenches 40U/40L (not shown), for example with respect to “gate-first” processing.

A charge-blocking region (e.g., charge-blocking material 30) is between storage material 32 and individual control-gate regions 52. A charge block may have the following functions in a memory cell: In a program mode, the charge block may prevent charge carriers from passing out of the storage material (e.g., floating-gate material, charge-trapping material, etc.) toward the control gate, and in an erase mode the charge block may prevent charge carriers from flowing into the storage material from the control gate. Accordingly, a charge block may function to block charge migration between the control-gate region and the storage material of individual memory cells. An example charge-blocking region as shown comprises insulator material 30. By way of further examples, a charge-blocking region may comprise a laterally (e.g., radially) outer portion of the storage material (e.g., material 32) where such storage material is insulative (e.g., in the absence of any different-composition material between an insulative storage material 32 and conducting material 48). Regardless, as an additional example, an interface of a storage material and conductive material of a control gate may be sufficient to function as a charge-blocking region in the absence of any separate-composition-insulator material 30. Further, an interface of conducting material 48 with material 30 (when present) in combination with insulator material 30 may together function as a charge-blocking region, and as alternately or additionally may a laterally-outer region of an insulative storage material (e.g., a silicon nitride material 32). An example material 30 is one or more of silicon hafnium oxide and silicon dioxide.

Intervening material 57 has been formed in trenches 40U/40L and thereby laterally-between and longitudinally-along immediately-laterally-adjacent memory blocks 58. Intervening material 57 may provide lateral electrical isolation (insulation) between immediately-laterally-adjacent memory blocks. Such may include one or more of insulative, semiconductive, and conducting materials and, regardless, may facilitate conductive tiers 22 from shorting relative one another in a finished circuitry construction. Example insulative materials are one or more of SiO₂, Si₃N₄, Al₂O₃, and undoped polysilicon. Intervening material 57 may include through array vias (not shown).

Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used in the embodiments shown and described with reference to the above embodiments.

FIG. 21 shows an example alternate embodiment construction 10 a in comparison to that of construction 10 of FIG. 17. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “a” or with different numerals. Intervening tier 21 a in construction 10 a is of the same thickness as tiers 22U/22L and 20U/20L immediately there-above and there-below. Such may result, for example, from modifying construction 10 in FIG. 2 to have intervening tier 21 a and otherwise proceeding with the method described herein. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

Although not so limited, some aspects of the invention were motivated in overcoming problems associated with formation of charge-blocking material 30 as an oxide. In some methods, remaining presence of radially-outer silicon dioxide 70 of sacrificial material 59 in lower channel openings 25L facilitates formation of a charge-blocking oxide material 30. Etching of upper channel openings 39 to sacrificial material 59 in lower channel openings 25L previously had a tendency to etch away much of radially-outer silicon dioxide 70 leading to gaps where charge-blocking oxide material 30 would not form using such methods. Forming an intervening tier 21 or 21 a as described herein may reduce or eliminate such problems.

Alternate embodiment constructions may result from method embodiments described above, or otherwise. Regardless, embodiments of the invention encompass memory arrays independent of method of manufacture. Nevertheless, such memory arrays may have any of the attributes as described herein in method embodiments. Likewise, the above-described method embodiments may incorporate, form, and/or have any of the attributes described with respect to device embodiments.

In one embodiment, a memory array (e.g., 12) comprising strings (e.g., 49) of memory cells (e.g., 56) comprises an upper stack (e.g., 18U) above a lower stack (e.g., 18L). The lower stack comprises vertically-alternating lower conductive tiers (e.g., 22L) and lower insulative tiers (e.g., 20L). The upper stack comprises vertically-alternating upper conductive tiers (e.g., 22U) and upper insulative tiers (e.g., 20U). An intervening tier (e.g., 21 or 21 a) is vertically between the upper and lower stacks. The intervening tier is at least predominantly polysilicon and of different composition from compositions of the upper conductive tier and the upper insulative tier immediately-above the intervening tier and of different composition from compositions of the lower conductive tier and the lower insulative tier immediately-below the intervening tier. Channel-material strings (e.g., 53) of memory cells (e.g., 56) extend through the upper stack, the intervening tier, and the lower stack. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

In one embodiment, a memory array (e.g., 12) comprising strings (e.g., 49) of memory cells (e.g., 56) comprises an upper stack (e.g., 18U) above a lower stack (e.g., 18L). The lower stack comprises vertically-alternating lower conductive tiers (e.g., 22L) and lower insulative tiers (e.g., 20L). The upper stack comprises vertically-alternating upper conductive tiers (e.g., 22U) and upper insulative tiers (e.g., 20U). An intervening tier (e.g., 21 or 21 a) is vertically between the upper and lower stacks. The intervening tier is at least predominantly conductive and of different composition from composition of the upper conductive tier immediately-above the intervening tier and of different composition from composition of the lower conductive tier immediately-below the intervening tier. Channel-material strings (e.g., 53) of memory cells (e.g., 56) extend through the upper stack, the intervening tier, and the lower stack. In one embodiment, the intervening tier is at least predominantly at least one of an elemental metal, a metal alloy, a metal nitride, and a metal silicide. In another embodiment, the intervening tier is at least predominantly conductively-doped semiconductive material.

In one embodiment, conductive material of the intervening tier is directly against conducting material of the upper conductive tier immediately-above the intervening tier and is directly against the lower conductor tier immediately-below the intervening tier In one such embodiment, each of the conductive material, the conducting material, and the conductor material is metal material, and in one such latter embodiment the metal material is at least predominantly at least one of an elemental metal, a metal alloy, a metal nitride, and a metal silicide.

Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

In one embodiment, a memory array (e.g., 12) comprising strings (e.g., 49) of memory cells (e.g., 56) comprises an upper stack (e.g., 18U) above a lower stack (e.g., 18L). The lower stack comprises vertically-alternating lower conductive tiers (e.g., 22L) and lower insulative tiers (e.g., 20L). The upper stack comprises vertically-alternating upper conductive tiers (e.g., 22U) and upper insulative tiers (e.g., 20U). An intervening tier [e.g., 21 or 21 a, and regardless of whether having any of the (a), (b), and/or (c) attributes] is vertically between the upper and lower stacks. Channel-material strings (e.g., 53) of memory cells (e.g., 56) extend through the upper stack, the intervening tier, and the lower stack. That portion of individual of the channel-material strings in the upper stack has an average longitudinal axis (e.g., 85) that is angled from an average longitudinal axis (e.g., 75) of that portion of the individual channel-material strings in the lower stack. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

The above processing(s) or construction(s) may be considered as being relative to an array of components formed as or within two stacks or two decks of such components above or as part of an underlying base substrate (albeit, the two stacks/decks may each have multiple tiers). Control and/or other peripheral circuitry for operating or accessing such components within an array may also be formed anywhere as part of the finished construction, and in some embodiments may be under the array (e.g., CMOS under-array). Regardless, one or more additional such stack(s)/deck(s) may be provided or fabricated above and/or below that shown in the figures or described above. Further, the array(s) of components may be the same or different relative one another in different stacks/decks and different stacks/decks may be of the same thickness or of different thicknesses relative one another. Intervening structure may be provided between immediately-vertically-adjacent stacks/decks (e.g., additional circuitry and/or dielectric layers). Also, different stacks/decks may be electrically coupled relative one another. The multiple stacks/decks may be fabricated separately and sequentially (e.g., one atop another), or two or more stacks/decks may be fabricated at essentially the same time.

The assemblies and structures discussed above may be used in integrated circuits/circuitry and may be incorporated into electronic systems. Such electronic systems may be used in, for example, memory modules, device drivers, power modules, communication modems, processor modules, and application-specific modules, and may include multilayer, multichip modules. The electronic systems may be any of a broad range of systems, such as, for example, cameras, wireless devices, displays, chip sets, set top boxes, games, lighting, vehicles, clocks, televisions, cell phones, personal computers, automobiles, industrial control systems, aircraft, etc.

In this document unless otherwise indicated, “elevational”, “higher”, “upper”, “lower”, “top”, “atop”, “bottom”, “above”, “below”, “under”, “beneath”, “up”, and “down” are generally with reference to the vertical direction. “Horizontal” refers to a general direction (i.e., within 10 degrees) along a primary substrate surface and may be relative to which the substrate is processed during fabrication, and vertical is a direction generally orthogonal thereto. Reference to “exactly horizontal” is the direction along the primary substrate surface (i.e., no degrees there-from) and may be relative to which the substrate is processed during fabrication. Further, “vertical” and “horizontal” as used herein are generally perpendicular directions relative one another and independent of orientation of the substrate in three-dimensional space. Additionally, “elevationally-extending” and “extend(ing) elevationally” refer to a direction that is angled away by at least 45° from exactly horizontal. Further, “extend(ing) elevationally”, “elevationally-extending”, “extend(ing) horizontally”, “horizontally-extending” and the like with respect to a field effect transistor are with reference to orientation of the transistor's channel length along which current flows in operation between the source/drain regions. For bipolar junction transistors, “extend(ing) elevationally” “elevationally-extending”, “extend(ing) horizontally”, “horizontally-extending” and the like, are with reference to orientation of the base length along which current flows in operation between the emitter and collector. In some embodiments, any component, feature, and/or region that extends elevationally extends vertically or within 10° of vertical.

Further, “directly above”, “directly below”, and “directly under” require at least some lateral overlap (i.e., horizontally) of two stated regions/materials/components relative one another. Also, use of “above” not preceded by “directly” only requires that some portion of the stated region/material/component that is above the other be elevationally outward of the other (i.e., independent of whether there is any lateral overlap of the two stated regions/materials/components). Analogously, use of “below” and “under” not preceded by “directly” only requires that some portion of the stated region/material/component that is below/under the other be elevationally inward of the other (i.e., independent of whether there is any lateral overlap of the two stated regions/materials/components).

Any of the materials, regions, and structures described herein may be homogenous or non-homogenous, and regardless may be continuous or discontinuous over any material which such overlie. Where one or more example composition(s) is/are provided for any material, that material may comprise, consist essentially of, or consist of such one or more composition(s). Further, unless otherwise stated, each material may be formed using any suitable existing or future-developed technique, with atomic layer deposition, chemical vapor deposition, physical vapor deposition, epitaxial growth, diffusion doping, and ion implanting being examples.

Additionally, “thickness” by itself (no preceding directional adjective) is defined as the mean straight-line distance through a given material or region perpendicularly from a closest surface of an immediately-adjacent material of different composition or of an immediately-adjacent region. Additionally, the various materials or regions described herein may be of substantially constant thickness or of variable thicknesses. If of variable thickness, thickness refers to average thickness unless otherwise indicated, and such material or region will have some minimum thickness and some maximum thickness due to the thickness being variable. As used herein, “different composition” only requires those portions of two stated materials or regions that may be directly against one another to be chemically and/or physically different, for example if such materials or regions are not homogenous. If the two stated materials or regions are not directly against one another, “different composition” only requires that those portions of the two stated materials or regions that are closest to one another be chemically and/or physically different if such materials or regions are not homogenous. In this document, a material, region, or structure is “directly against” another when there is at least some physical touching contact of the stated materials, regions, or structures relative one another. In contrast, “over”, “on”, “adjacent”, “along”, and “against” not preceded by “directly” encompass “directly against” as well as construction where intervening material(s), region(s), or structure(s) result(s) in no physical touching contact of the stated materials, regions, or structures relative one another.

Herein, regions-materials-components are “electrically coupled” relative one another if in normal operation electric current is capable of continuously flowing from one to the other and does so predominately by movement of subatomic positive and/or negative charges when such are sufficiently generated. Another electronic component may be between and electrically coupled to the regions-materials-components. In contrast, when regions-materials-components are referred to as being “directly electrically coupled”, no intervening electronic component (e.g., no diode, transistor, resistor, transducer, switch, fuse, etc.) is between the directly electrically coupled regions-materials-components.

Any use of “row” and “column” in this document is for convenience in distinguishing one series or orientation of features from another series or orientation of features and along which components have been or may be formed. “Row” and “column” are used synonymously with respect to any series of regions, components, and/or features independent of function. Regardless, the rows may be straight and/or curved and/or parallel and/or not parallel relative one another, as may be the columns. Further, the rows and columns may intersect relative one another at 90° or at one or more other angles (i.e., other than the straight angle).

The composition of any of the conductive/conductor/conducting materials herein may be metal material and/or conductively-doped semiconductive/semiconductor/semiconducting material. “Metal material” is any one or combination of an elemental metal, any mixture or alloy of two or more elemental metals, and any one or more conductive metal compound(s).

Herein, any use of “selective” as to etch, etching, removing, removal, depositing, forming, and/or formation is such an act of one stated material relative to another stated material(s) so acted upon at a rate of at least 2:1 by volume. Further, any use of selectively depositing, selectively growing, or selectively forming is depositing, growing, or forming one material relative to another stated material or materials at a rate of at least 2:1 by volume for at least the first 75 Angstroms of depositing, growing, or forming.

Unless otherwise indicated, use of “or” herein encompasses either and both.

CONCLUSION

In some embodiments, a method used in forming a memory array comprising strings of memory cells comprises forming an upper stack above a lower stack. The lower stack comprises vertically-alternating lower first tiers and lower second tiers. The upper stack comprises vertically-alternating upper first tiers and upper second tiers. An intervening tier is vertically between the upper and lower stacks. Lower channel openings extend through the intervening tier and the lower first and second tiers. The lower channel openings have sacrificial material therein in the intervening tier and in the lower first and second tiers. The intervening tier is at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier. Upper channel openings are formed through the upper first and second tiers to the intervening tier. Individual of the upper channel openings extend to the sacrificial material in individual of the lower channel openings. The sacrificial material is removed from the individual lower channel openings through the upper channel openings and thereafter channel-material strings are formed in the upper and lower channel openings.

In some embodiments, a memory array comprising strings of memory cells comprises an upper stack above a lower stack. The lower stack comprises vertically-alternating lower conductive tiers and lower insulative tiers. The upper stack comprises vertically-alternating upper conductive tiers and upper insulative tiers. An intervening tier is vertically between the upper and lower stacks. The intervening tier is at least predominantly polysilicon and of different composition from compositions of the upper conductive tier and the upper insulative tier immediately-above the intervening tier and of different composition from compositions of the lower conductive tier and the lower insulative tier immediately-below the intervening tier. Channel-material strings of memory cells extend through the upper stack, the intervening tier, and the lower stack.

In some embodiments, a memory array comprising strings of memory cells comprises an upper stack above a lower stack. The lower stack comprises vertically-alternating lower conductive tiers and lower insulative tiers. The upper stack comprises vertically-alternating upper conductive tiers and upper insulative tiers. An intervening tier is vertically between the upper and lower stacks. The intervening tier is at least predominantly conductive and of different composition from composition of the upper conductive tier immediately-above the intervening tier and of different composition from composition of the lower conductive tier immediately-below the intervening tier. Channel-material strings of memory cells extend through the upper stack, the intervening tier, and the lower stack.

In some embodiments, a memory array comprising strings of memory cells comprises an upper stack above a lower stack. The lower stack comprises vertically-alternating lower conductive tiers and lower insulative tiers. The upper stack comprises vertically-alternating upper conductive tiers and upper insulative tiers. An intervening tier is vertically between the upper and lower stacks. Channel-material strings of memory cells extend through the upper stack, the intervening tier, and the lower stack. That portion of individual of the channel-material strings in the upper stack has an average longitudinal axis that is angled from an average longitudinal axis of that portion of the individual channel-material strings in the lower stack.

In some embodiments, a memory array comprising strings of memory cells comprises an upper stack above a lower stack. The lower stack comprises vertically-alternating lower conductive tiers and lower insulative tiers. The upper stack comprises vertically-alternating upper conductive tiers and upper insulative tiers. An intervening tier is vertically between the upper and lower stacks. The intervening tier is at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper conductive tier and that of the upper insulative tier immediately-above the intervening tier and greater than that of the lower conductive tier and that of the lower insulative tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper conductive tier and the upper insulative tier immediately-above the intervening tier and of different composition from compositions of the lower conductive tier and the lower insulative tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the composition of the upper conductive tier immediately-above the intervening tier and of different composition from the composition of the lower conductive tier immediately-below the intervening tier. Channel-material strings of memory cells extend through the upper stack, the intervening tier, and the lower stack. That portion of individual of the channel-material strings in the upper stack has an average longitudinal axis that is angled from an average longitudinal axis of that portion of the individual channel-material strings in the lower stack.

In compliance with the statute, the subject matter disclosed herein has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the claims are not limited to the specific features shown and described, since the means herein disclosed comprise example embodiments. The claims are thus to be afforded full scope as literally worded, and to be appropriately interpreted in accordance with the doctrine of equivalents. 

The invention claimed is:
 1. A method used in forming a memory array comprising strings of memory cells, comprising: forming an upper stack above a lower stack, the lower stack comprising vertically-alternating lower first tiers and lower second tiers, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, an intervening tier vertically between the upper and lower stacks, lower channel openings extending through the intervening tier and the lower first and second tiers, the lower channel openings having sacrificial material therein in the intervening tier and in the lower first and second tiers, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier; forming upper channel openings through the upper first and second tiers to the intervening tier, individual of the upper channel openings extending to the sacrificial material in individual of the lower channel openings; removing the sacrificial material from the individual lower channel openings through the upper channel openings and thereafter forming channel-material strings in the upper and lower channel openings; and the sacrificial material comprises a radially-outer silicon dioxide, a radially-inner silicon dioxide, and aluminum oxide radially-between the radially-outer silicon dioxide and the radially-inner silicon dioxide.
 2. The method of claim 1 wherein the radially-outer silicon dioxide and the radially-inner silicon dioxide are of different composition relative one another.
 3. The method of claim 2 wherein the different composition is characterized by concentration of at least one of boron and phosphorus.
 4. A method used in forming a memory array comprising strings of memory cells, comprising: forming an upper stack above a lower stack, the lower stack comprising vertically-alternating lower first tiers and lower second tiers, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, an intervening tier vertically between the upper and lower stacks, lower channel openings extending through the intervening tier and the lower first and second tiers, the lower channel openings having sacrificial material therein in the intervening tier and in the lower first and second tiers, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier; forming upper channel openings through the upper first and second tiers to the intervening tier, individual of the upper channel openings extending to the sacrificial material in individual of the lower channel openings; removing the sacrificial material from the individual lower channel openings through the upper channel openings and thereafter forming channel-material strings in the upper and lower channel openings; and the at least one of (a), (b), and (c) being (b).
 5. A method used in forming a memory array comprising strings of memory cells, comprising: forming an upper stack above a lower stack, the lower stack comprising vertically-alternating lower first tiers and lower second tiers, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, an intervening tier vertically between the upper and lower stacks, lower channel openings extending through the intervening tier and the lower first and second tiers, the lower channel openings having sacrificial material therein in the intervening tier and in the lower first and second tiers, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier; forming upper channel openings through the upper first and second tiers to the intervening tier, individual of the upper channel openings extending to the sacrificial material in individual of the lower channel openings; removing the sacrificial material from the individual lower channel openings through the upper channel openings and thereafter forming channel-material strings in the upper and lower channel openings; and the at least one of (a), (b), and (c) being (c).
 6. A method used in forming a memory array comprising strings of memory cells, comprising: forming an upper stack above a lower stack, the lower stack comprising vertically-alternating lower first tiers and lower second tiers, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, an intervening tier vertically between the upper and lower stacks, lower channel openings extending through the intervening tier and the lower first and second tiers, the lower channel openings having sacrificial material therein in the intervening tier and in the lower first and second tiers, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier; forming upper channel openings through the upper first and second tiers to the intervening tier, individual of the upper channel openings extending to the sacrificial material in individual of the lower channel openings; removing the sacrificial material from the individual lower channel openings through the upper channel openings and thereafter forming channel-material strings in the upper and lower channel openings; and the at least one of (a), (b), and (c) being at least two of (a), (b), and (c).
 7. A method used in forming a memory array comprising strings of memory cells, comprising: forming an upper stack above a lower stack, the lower stack comprising vertically-alternating lower first tiers and lower second tiers, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, an intervening tier vertically between the upper and lower stacks, lower channel openings extending through the intervening tier and the lower first and second tiers, the lower channel openings having sacrificial material therein in the intervening tier and in the lower first and second tiers, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier; forming upper channel openings through the upper first and second tiers to the intervening tier, individual of the upper channel openings extending to the sacrificial material in individual of the lower channel openings; removing the sacrificial material from the individual lower channel openings through the upper channel openings and thereafter forming channel-material strings in the upper and lower channel openings; and the at least one of (a), (b), and (c) being (a), (b), and (c).
 8. A method used in forming a memory array comprising strings of memory cells, comprising: forming an upper stack above a lower stack, the lower stack comprising vertically-alternating lower first tiers and lower second tiers, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, an intervening tier vertically between the upper and lower stacks, lower channel openings extending through the intervening tier and the lower first and second tiers, the lower channel openings having sacrificial material therein in the intervening tier and in the lower first and second tiers, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper first tier and that of the upper second tier immediately-above the intervening tier and greater than that of the lower first tier and that of the lower second tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from compositions of the lower first tier and the lower second tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the compositions of the upper first tier and the upper second tier immediately-above the intervening tier and of different composition from the compositions of the lower first tier and the lower second tier immediately-below the intervening tier; forming upper channel openings through the upper first and second tiers to the intervening tier, individual of the upper channel openings extending to the sacrificial material in individual of the lower channel openings; removing the sacrificial material from the individual lower channel openings through the upper channel openings and thereafter forming channel-material strings in the upper and lower channel openings; and the individual upper channel openings are formed to have an average longitudinal axis that is angled from an average longitudinal axis of their respective individual lower channel opening to which they extend.
 9. The method of claim 8 wherein said angled is an angle of at least 0.5° from the average longitudinal axis of their respective individual lower channel opening.
 10. The method of claim 8 wherein said angled is an angle of no more than 5.0° from the average longitudinal axis of their respective individual lower channel opening.
 11. The method of claim 8 wherein said angled is an angle of at least 1.0° to no more than 5.0° from the average longitudinal axis of their respective individual lower channel opening.
 12. A memory array comprising strings of memory cells, comprising: an upper stack above a lower stack, the lower stack comprising vertically-alternating lower conductive tiers and lower insulative tiers, the upper stack comprising vertically-alternating upper conductive tiers and upper insulative tiers; an intervening tier vertically between the upper and lower stacks; and channel-material strings of memory cells extending through the upper stack, the intervening tier, and the lower stack; that portion of individual of the channel-material strings in the upper stack having an average longitudinal axis that is angled from an average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 13. The memory array of claim 12 wherein said angled is an angle of at least 0.5° from the average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 14. The memory array of claim 12 wherein said angled is an angle of no more than 5.0° from the average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 15. The memory array of claim 12 wherein said angled is an angle of at least 1.0° to no more than 5.0° from the average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 16. A memory array comprising strings of memory cells, comprising: an upper stack above a lower stack, the lower stack comprising vertically-alternating lower conductive tiers and lower insulative tiers, the upper stack comprising vertically-alternating upper conductive tiers and upper insulative tiers; an intervening tier vertically between the upper and lower stacks, the intervening tier being at least one of (a), (b), and (c), where: (a): of a thickness greater than that of the upper conductive tier and that of the upper insulative tier immediately-above the intervening tier and greater than that of the lower conductive tier and that of the lower insulative tier immediately-below the intervening tier; (b): at least predominantly polysilicon and of different composition from compositions of the upper conductive tier and the upper insulative tier immediately-above the intervening tier and of different composition from compositions of the lower conductive tier and the lower insulative tier immediately-below the intervening tier; and (c): at least predominantly conductive and of different composition from the composition of the upper conductive tier immediately-above the intervening tier and of different composition from the composition of the lower conductive tier immediately-below the intervening tier; and channel-material strings of memory cells extending through the upper stack, the intervening tier, and the lower stack; that portion of individual of the channel-material strings in the upper stack having an average longitudinal axis that is angled from an average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 17. The memory array of claim 16 being (a).
 18. The memory array of claim 16 being (b).
 19. The memory array of claim 16 being (c).
 20. The memory array of claim 16 being at least two of (a), (b), and (c).
 21. The memory array of claim 16 being (a), (b), and (c).
 22. The memory array of claim 16 wherein said angled is an angle of at least 0.5° from the average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 23. The memory array of claim 16 wherein said angled is an angle of no more than 5.0° from the average longitudinal axis of that portion of the individual channel-material strings in the lower stack.
 24. The memory array of claim 16 wherein said angled is an angle of at least 1.0° to no more than 5.0° from the average longitudinal axis of that portion of the individual channel-material strings in the lower stack. 